At the age of seventeen, he moved to Cardiff,[8] where he studied under the supervision of Louise Ryan, an established singing coach.[9] In 1997 he won a scholarship to The London Studio Centre in Kings Cross, London.[10] He graduated in 2000.

In 2008, he landed his most significant theatre role playing Vincent in the play Small Change written and directed by Peter Gill at the Donmar Warehouse, it was significant in that he gained recognition from film casting directors and US agencies from this play and he was also nominated for the Evening Standard award for best newcomer because of his performance in Small Change. Later that same year he did his second show at the Donmar Warehouse, Piaf, in which he played Yves Montand.

Evans played the Musketeer Aramis in Paul W. S. Anderson's version of The Three Musketeers (filmed in 2010 and released in 2011). He was cast in a lead role in Tarsem Singh's Greek epic, Immortals (2011), in which he played the King of the Gods, Zeus. And at the end of 2010, he took a role opposite John Cusack in James McTeigue's film The Raven, replacing Jeremy Renner. In the film, released in 2012 and set in mid-19th century Baltimore, Evans played Detective Emmett Fields, who investigates a series of murders alongside Cusack's Edgar Allan Poe.[11] Shooting took place in Budapest and Serbia in November 2010.

Evans is openly gay. In a 2002 interview, he said, "Everybody knew me as a gay man, and in my life in London I never tried to hide it," and that by being open he would not have "that skeleton in the closet they can rattle out".[18] In 2004, he said his acting career had not suffered by being out.[19] In 2014, Evans acknowledged the importance of marketability, and that, although he does not hide his homosexuality, he is reticent to discuss it with the media.[20]